Subsidiary Information - Condensed Consolidating Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Revenues
Net earned premiums	$ 192	$ 213	$ 219	$ 142	$ 158	$ 144	$ 136	$ 132	$ 766	[1]	$ 570	[1]	$ 752	[1]
Net investment income	112	112	98	101	102	102	96	103	423		403		393
Net realized investment gains (losses)	(6)	(27)	(9)	16	(35)	(19)	(8)	2	(26)		(60)		52
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements									(18)		23		(42)
Net unrealized gains (losses)									746		800		107
Net change in fair value of credit derivatives	428	86	90	124	676	255	103	(211)	728		823		65
Bargain purchase gain and settlement of pre-existing relationships	0	0	214	0	0	0	0	0	214		0		0
Other									102		258		346
Total revenues									2,207		1,994		1,608
Expenses
Loss and LAE	106	112	188	18	72	(44)	57	41	424		126		154
Amortization of DAC	5	5	6	4	13	4	3	5	20		25		12
Interest expense	25	25	26	25	25	27	20	20	101		92		82
Other operating expenses	55	54	66	56	55	50	55	60	231		220		218
Total expenses									776		463		466
Income (loss) before income taxes	584	172	409	266	756	488	218	69	1,431		1,531		1,142
Total (provision) benefit for income taxes	(155)	(43)	(112)	(65)	(224)	(133)	(59)	(27)	(375)		(443)		(334)
Equity in net earnings of subsidiaries									0		0		0
Net income (loss)									1,056		1,088		808
Less: noncontrolling interest									0		0		0
Net income (loss)	$ 429	$ 129	$ 297	$ 201	$ 532	$ 355	$ 159	$ 42	1,056		1,088		808
Comprehensive income (loss)									923		1,298		453
Reportable Legal Entities [Member] | Assured Guaranty Ltd. (Parent) [Member]
Revenues
Net earned premiums									0		0		0
Net investment income									0		0		0
Net realized investment gains (losses)									0		0		0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements									0		0		0
Net unrealized gains (losses)									0		0		0
Net change in fair value of credit derivatives									0		0		0
Bargain purchase gain and settlement of pre-existing relationships									0
Other									0		0		0
Total revenues									0		0		0
Expenses
Loss and LAE									0		0		0
Amortization of DAC									0		0		0
Interest expense									0		0		0
Other operating expenses									30		31		22
Total expenses									30		31		22
Income (loss) before income taxes									(30)		(31)		(22)
Total (provision) benefit for income taxes									0		0		0
Equity in net earnings of subsidiaries									1,086		1,119		830
Net income (loss)									1,056		1,088		808
Less: noncontrolling interest									0		0		0
Net income (loss)									1,056		1,088		808
Comprehensive income (loss)									923		1,298		453
Reportable Legal Entities [Member] | AGUS (Issuer) [Member]
Revenues
Net earned premiums									0		0		0
Net investment income									1		0		0
Net realized investment gains (losses)									0		0		0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements									0		0		0
Net unrealized gains (losses)									0		0		0
Net change in fair value of credit derivatives									0		0		0
Bargain purchase gain and settlement of pre-existing relationships									0
Other									0		0		0
Total revenues									1		0		0
Expenses
Loss and LAE									0		0		0
Amortization of DAC									0		0		0
Interest expense									52		40		28
Other operating expenses									1		1		1
Total expenses									53		41		29
Income (loss) before income taxes									(52)		(41)		(29)
Total (provision) benefit for income taxes									18		14		9
Equity in net earnings of subsidiaries									923		983		768
Net income (loss)									889		956		748
Less: noncontrolling interest									0		0		0
Net income (loss)									889		956		748
Comprehensive income (loss)									787		1,114		522
Reportable Legal Entities [Member] | AGMH (Issuer) [Member]
Revenues
Net earned premiums									0		0		0
Net investment income									0		1		1
Net realized investment gains (losses)									1		0		0
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements									0		0		0
Net unrealized gains (losses)									0		0		0
Net change in fair value of credit derivatives									0		0		0
Bargain purchase gain and settlement of pre-existing relationships									0
Other									0		0		0
Total revenues									1		1		1
Expenses
Loss and LAE									0		0		0
Amortization of DAC									0		0		0
Interest expense									54		54		54
Other operating expenses									1		1		1
Total expenses									55		55		55
Income (loss) before income taxes									(54)		(54)		(54)
Total (provision) benefit for income taxes									19		19		17
Equity in net earnings of subsidiaries									468		513		701
Net income (loss)									433		478		664
Less: noncontrolling interest									0		0		0
Net income (loss)									433		478		664
Comprehensive income (loss)									359		577		515
Reportable Legal Entities [Member] | Other Entities [Member]
Revenues
Net earned premiums									783		566		740
Net investment income									432		412		408
Net realized investment gains (losses)									(19)		(58)		87
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements									(18)		23		(42)
Net unrealized gains (losses)									773		800		107
Net change in fair value of credit derivatives									755		823		65
Bargain purchase gain and settlement of pre-existing relationships									54
Other									102		259		348
Total revenues									2,107		2,002		1,648
Expenses
Loss and LAE									434		122		144
Amortization of DAC									29		33		12
Interest expense									14		16		20
Other operating expenses									202		195		199
Total expenses									679		366		375
Income (loss) before income taxes									1,428		1,636		1,273
Total (provision) benefit for income taxes									(365)		(469)		(387)
Equity in net earnings of subsidiaries									39		32		19
Net income (loss)									1,102		1,199		905
Less: noncontrolling interest									39		32		19
Net income (loss)									1,063		1,167		886
Comprehensive income (loss)									967		1,570		309
Consolidating Adjustments [Member]
Revenues
Net earned premiums									(17)		4		12
Net investment income									(10)		(10)		(16)
Net realized investment gains (losses)									(8)		(2)		(35)
Net change in fair value of credit derivatives:
Realized gains (losses) and other settlements									0		0		0
Net unrealized gains (losses)									(27)		0		0
Net change in fair value of credit derivatives									(27)		0		0
Bargain purchase gain and settlement of pre-existing relationships									160
Other									0		(1)		(2)
Total revenues									98		(9)		(41)
Expenses
Loss and LAE									(10)		4		10
Amortization of DAC									(9)		(8)		0
Interest expense									(19)		(18)		(20)
Other operating expenses									(3)		(8)		(5)
Total expenses									(41)		(30)		(15)
Income (loss) before income taxes									139		21		(26)
Total (provision) benefit for income taxes									(47)		(7)		27
Equity in net earnings of subsidiaries									(2,516)		(2,647)		(2,318)
Net income (loss)									(2,424)		(2,633)		(2,317)
Less: noncontrolling interest									(39)		(32)		(19)
Net income (loss)									(2,385)		(2,601)		(2,298)
Comprehensive income (loss)									$ (2,113)		$ (3,261)		$ (1,346)

[1] Excludes $21 million, $32 million and $60 million for the year ended December 31, 2015, 2014 and 2013, respectively, related to consolidated FG VIEs.